Background: Community-acquired pneumonia (CAP) is a serious health problem in Chile. Aim: To study prognostic factors on admission and outcome of CAP, in immune competent adult patients, hospitalized in the Catholic University Clinical Hospital. Patients and methods: All adult patients admitted with a CAP in a period of 2 years were prospectively studied. Patients with immunodeficiency, solid tumors or receiving oral adrenal steroids were excluded from the study. Results: In the study period, 463 patients (69±19 years, 55% male) were evaluated. Ninety four percent were treated with 2nd or 3rd generation cephalosporins. Mean hospital length of stay was 10 days. Mortality during hospital stay was 8% and in the ensuing 30 days, it was 12%. Bacterial etiology was established in 25% of cases. The most frequent pathogens isolated were Streptococcus pneumoniae (10.2%), Haemophilus influenzae (3.7%), Staphylococcus aureus (2.8%) and Gram negative bacilli (5.2%). Admission prognostic factors associated with hospital mortality were: an age over 65 years, presence of comorbidity, chronic neurological and hepatic disease, suspicion of aspiration, duration of symptoms for less than 3 days, presence of dyspnea and altered mental status, absence of cough, fever and chills; low blood pressure, tachypnea, metabolic acidosis, hypoxemia, high blood urea nitrogen, hypernatremia, hyperkalemia, hyperphosphatemia, hypoalbuminemia, multilobar radiographic pulmonary infiltrates, bacteremia, high risk categories of the Fine Index (IV and V), and admission to Intermediate Care Unit or ICU. Conclusions: The features of community acquired pneumonia of these patients are similar to those reported abroad (Rev Méd Chile 2002; 130: 1373-82).